The goal of this project in the Baltimore Longitudinal Study of Aging is to characterize the age-related changes in bone mass and body composition that have been demonstrated in both men and women. Age and sex related differences hormones, nutritional and physiological variables involved in bone turnover are important in elucidating changes in bone physiology in normal aging and disease. Specifically, the relationships of age and sex to changes in body composition, both as a marker of obesity and as a measure of the weight-bearing load on bone are important factors in bone status and rates of change. The most dramatic rates of change in bone mass occur at the menopause, and changes of body composition, bone mass, and bone markers and hormones are being investigated in 114 women aged 45-55 who have been recruited to the Baltimore Longitudinal Study of Aging as part of the perimenopausal cohort. The women, who were still menstruating, on entry to the study, are followed at 3month intervals as they traverse the menopause, and for two years since their last period. The studies will allow for the interpretation of the changes that occur prior to and mmediately around the time of the cessation of menses, changes that can only be appreciated in a prospective longitudinal study. The follow-up of the 10-15 women who had not entered their menopause was terminated this year. Analyses examining the relationship of hormonal changes across the menopause period and bone and body composition changes will continue over the next year.